Abstract
THE factors determining the onset of labour are largely unknown, though the regulating mechanisms seem to originate from both the foetus and the mother. The foetus seems to determine the day of birth, through the maturation of the pituitary–adrenal–placental axis, but the mother may provide a fine control, determining the precise hour of birth. Labour varies greatly in its timing and speed of execution, presumably as the result of selection to ensure the maximum probability of survival of both the mother and offspring. Environmental factors such as light, tides and predators are of great importance, providing cues which influence the final hour of birth. Even women, who during childbirth are confined in a most artificial environment, show a marked tendency to deliver in the early hours of the morning1–4.
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LINCOLN, D., PORTER, D. Timing of the photoperiod and the hour of birth in rats. Nature 260, 780–781 (1976). https://doi.org/10.1038/260780a0
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DOI: https://doi.org/10.1038/260780a0
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